Stepping device

ABSTRACT

Stepping device for a comptometer provided with a ratchet wheel and a pawl. An oscillating or reciprocating movement of the pawl is changed to a unidirectional rotary movement of the ratchet wheel. The pawl is forked or bifurcated to form shanks on diametrical opposite sides of the ratchet wheel, which shanks are each provided with a projection cooperating with the teeth of the ratchet wheel. A least one of the shanks is provided with another projection situated at a circumferential distance from the projection on the same shank which is greater than the gear pitch of the ratchet wheel and so chosen that when the two projections of the said shank are in contact with the sides or flanks of two teeth of the ratchet wheel then the resultant force of the forces acting at these sides is directed through the rotary axis of the ratchet wheel.

United States Patent Sahlgren et al. Mar. 7, 1972 [54] STEPPING DEVICE390,494 10/1888 Loud ..74/577 [72] Inventors: lloli A];SSEgremb'ZyLeMfxSB. :lngvar Wil- Primary Examiner wmiam R 0.1383

Janen an agen t 0 we en Assistant Examiner-Wesley S. Ratliff, Jr. [73]Assignee: Telefonaktiebolaget LM Ericsson, A!l0meyHane, & SPXecensStockholm, Sweden [57] ABSTRACT [22] Filed: Apr. 6, 1970 Stepping devicefor a comptometer provided with a ratchet pp 25,944 wheel and a pawl. Anoscillating or reciprocating movement of the pawl is changed to aunidirectional rotary movement of the ratchet wheel. The pawl is forkedor bifurcated to form [30] Fme'gn Apphcamm Pnomy Dam shanks ondiametrical opposite sides of the ratchet wheel, Apr. 23, 1969 Sweden..5777/69 ich hanks are each provided with a projection cooperating withthe teeth of the ratchet wheel. A least one of the shanks is [52] US. Cl..74/ 142, 74/577 M Provided with another Projection Situated a!circumfefemial 511 Im. Cl. ..G05g 1/00 distance from the Projection theSame Shank which is 58 Field of Search ..74/142 128 575, 577 greaterthan the gear Pitch the ratchet wheel and chose that when the twoprojections of the said shank are in contact with the sides or flanks oftwo teeth of the ratchet wheel then [56] Reieremes cued the resultantforce of the forces acting at these sides is UNITED STATES PATENTSdirected through the rotary axis of the ratchet wheel.

48,927 7/ l 865 Giroud ..74/577 3 Claims, 4 Drawing Figures PaUZNWEIJM7:912

INVENTORS Row A x: Smumm Bo Iuowm. wlumwu ATTORNEY STEPPING DEVICE Thepresent invention relates to a stepping device for a comptometerprovided with ratchet wheel and pawl, and more particularly to acomptometer in which an oscillating or reciprocating movement of thepawl is changed to a unidirectional rotary movement of the ratchetwheel.

With stepping devices of said type it is essential that the position ofthe ratchet wheel is well defined on completion of the steppingmovement. It can occur when shaping the pawl in a conventional mannerthat the ratchet wheel springs back to its starting position or that thepawl becomes wedged in the ratchet wheel and prevents faultless steppingforward at the next signal. The problem exists especially with suchcomptometers where, owing to considerations of space, there is arelatively short oscillation arm for the pawl.

The purpose of the present invention is to eliminate said drawbacks andto achieve a stepping device at which wedging between the ratchet wheeland the pawl is prevented and the position of the ratchet wheel after acompleted stepping is well defined.

The arrangement according to the invention is set forth in the appendedclaims.

The invention is described more in detail below by means of anembodiment with reference to the drawing in which:

FIG. 1 is a diagrammatic elevational view of a stepping device accordingto the invention in its rest position;

FIG. 2 is a fragmentary view of FIG. 1 in intermediate operationalposition upon energization of the magnet coil of the device;

FIG. 3 is a similar fragmentary view in a further advanced operationalposition; and

FIG. 4 is a similar fragmentary view in an operational position upondeenergization of the magnet coil.

In FIG. 1 a comptometer is shown, parts which have no direct connectionwith the invention, are only schematically indicated. A magnet coil 1when energized causes attraction of an armature 2 with a projection 3which interlocks with one end of a lever-formed pawl 4. The pawl isrevolving around an axis of rotation 5 which according to the example iscommon to the drive gear 6 of the comptometer but may consist of afulcrum pin. The other end of the pawl is bifurcated to form two shanksor forks 7 and 8 of which are situated on diametrically opposite sidesof a ratchet wheel 9 which according to the example is arranged on thesame axis 10 as the digit wheel 11 of the comptometer. The pawl need notnecessarily be open at its end but may consist of a closed ring-shapedpart, as is marked by broken lines, of and when construction points ofviews or 12 is qualities of the material make it advisable. A spring isfastened between a bracket 13 on the magnet coil and the pawl 4. Theshanks of the pawl are each provided with two inwardly extendingprojections l4, l5 and l6, 17 respectively which are positioned to makeengagement with the teeth of the ratchet wheel to turn the ratchetwheel. FIG. I shows the arrangement in its rest position. When themagnet works the pawl is turned upwards compared with the position shownin FIG. 1 due to the armature 2 being pulled downwards and pressing withits projection 3 the arm of the projection 16 on shank 8 downwards. FIG.2 shows the position where the pawl during the upward movement of thepawl has come in contact with a tooth 20 of the ratchet wheel. Duringthe continued reciprocating movement of the pawl the ratchet wheel isturned clockwise until another tooth 28 of the ratchet wheel countedcounterclockwise is in contact with the projection 17 also on the shank8 of the pawl. This position is indicated in FIG. 3. This figure alsoshows that the projections never fully occupy the spaces betweenadjacent teeth of the ratchet wheel. The ratchet wheel is retained inthis position as long as the magnet attracts armature 2. Thecircumferential distance between the projections 16 and 17 is chosen insuch a manner, that the distance is larger than a gear pitch of theratchet wheel in order to make possible that while the projection 16bears against the opposite blank of the tooth 20 counted in thecounterclockwise direction, the other projection 17 bears against theflank of the tooth 28 as the wheel 9 is turned in the clockwisedirection of rotation. In this manner it is assured that when theprojection 17 is engaged, the ratchet wheel stops in a well-definedposition. Simultaneously the resultant of the forces which occur at therespective contact points of the ratchet wheel, is directed in such amanner, that it extends roughly through the axis of rotation 10 of theratchet wheel. In this manner instability in the position of the ratchetwheel at the end of the movement of rotation is prevented as well aswedging between the pawl and the ratchet wheel. When the energization ofthe magnet ceases, the pawl 4 is brought back of the force of the spring12 acting upon the pawl in counterclockwise direction. First theprojection 15 comes in contact with the tooth 25 whereby the ratchetwheel 9 is turned in clockwise direction. This condition is shown inFIG. 4. The rotation can however only continue as long as the projection14 has not come in contact with the tooth 22. In the same manner as atthe shank 8 the distance and the mutual position between the projectionsare also here chosen in such a manner that the forces acting at thecontact positions of the projections 14 and 15 on the ratchet wheelproduce a resulting force which is directed roughly through the axis ofrotation 10 of the ratchet wheel. The last-mentioned condition appearsfrom FIG. 1. In other words the stepping device has returned to its restposition. It is not necessary that both shanks 7 and 8 are provided withstop projections 14 and 17 respectively. It may be enough to provide onea stop projection only on one shank; namely on the one which cooperateswith the ratchet wheel during the energization of the magnet coil of themagnet. The danger for wedging or unintentional change of the positionof the ratchet wheel is much larger at when the magnet coil is energizedthan when only the considerably smaller return force of the spring 12acts upon the pawl.

We claim:

1. In an electromagnetic comptometer a stepping device for converting alinear reciprocating movement to a unidirectional rotary movement, saidstepping device comprising:

a ratchet wheel;

' a common shaft seating said wheels for a joint rotation thereof;

an electromagnetic means selectively energizable;

a pivotally mounted two-armed pawl, one arm of said pawl constituting anarmature arranged to be attracted by said electromagnetic means uponenergization thereof thereby effecting a linear movement of said arm bypivoting the pawl, the other arm of the pawl being bifurcated therebyforming two shanks, said shanks being curved and positioned to encompassat least partly the outer peripheral outline of said ratchet wheelradially spaced apart therefrom, each of said shanks having thereon aninwardly protruding first projection engageable with valleys between theteeth of the wheel and one of said shanks having thereon a secondinwardly protruding projection also engageable with valleys between theteeth of the wheel, the first and the second projection on said oneshank being disposed at a circumferential spacing such that in responseto successive attractions and releases of the armature said firstprojection engages the counterclockwise facing flank of successive teeththereby causing incremental clockwise turning of the ratchet wheel andafter turning of said wheel into a predetermined angular position saidsecond projection engages the clockwise facing flank of a tooth therebylocking the ratchet wheel in said angular position when and while thearmature is attracted, of said first and said second projection engagingsaid respective counterclockwise and clockwise facing flanks of saidteeth of the ratchet wheel being also such that the forcessimultaneously applied by said projections to the flanks of therespective two teeth extend approximately through the rotational axis ofthe ratchet wheel; and

a return spring means attached to the pawl and biased to pivot the pawlin counterclockwise direction, said pivotal movement of the pawl causingengagement of the projection on the other shank with thecounterclockwise facing flank of a tooth upon deenergization of theelectromagnetic means thereby turning the ratchet wheel in clockwisedirection.

2. The stepping device according to claim 1 wherein a second projectionis provided on said other shank also, said second projection beingcorrelated with the first projection on the other shank so that bothsaid projections on the other shank simultaneously engage oppositelyfacing flanks of teeth in a second predetermined angular position of theratchet wheel thereby locking the wheel in said second angular position,the first and second projection on said other shank being so disposedthat the forces simultaneously applied to the flanks of the respectivetwo teeth also extend approximately through the rotational axis of theratchet wheel.

3. The stepping device according to claim I wherein the peripheraloutline of said projections on the shanks and of the valleys between theteeth of the ratchet wheel are so correlated that said protrusionsengage valleys with play thereby preventing jamming of the projectionsin the valleys.

i 1K i

1. In an electromagnetic comptometer a stepping device for converting alinear reciprocating movement to a unidirectional rotary movement, saidstepping device comprising: a ratchet wheel; a common shaft seating saidwheels for a joint rotation thereof; an electromagnetic meansselectively energizable; a pivotally mounted two-armed pawl, one arm ofsaid pawl constituting an armature arranged to be attracted by saidelectromagnetic means upon energization thereof thereby effecting alinear movement of said arm by pivoting the pawl, the other arm of thepawl being bifurcated thereby forming two shanks, said shanks beingcurved and positioned to encompass at least partly the outer peripheraloutline of said ratchet wheel radially spaced apart therefrom, each ofsaid shanks having thereon an inwardly protruding first projectionengageable with valleys between the teeth of the wheel and one of saidshanks having thereon a second inwardly protruding projection alsoengageable with valleys between the teeth of the wheel, the first andthe second projection on said one shank being disposed at acircumferential spacing such that in response to successive attractionsand releases of the armature said first projection engages thecounterclockwise facing flank of successive teeth thereby causingincremental clockwise turning of the ratchet wheel and after turning ofsaid wheel into a predetermined angular position said second projectionengages the clockwise facing flank of a tooth thereby locking theratchet wheel in said angular position when and while the armature isattracted, of said first and said second projection engaging saidrespective counterclockwise and clockwise facing flanks of said teeth ofthe ratchet wheel being also such that the forces simultaneously appliedby said projections to the flanks of the respective two teeth extendapproximately through the rotational axis of the ratchet wheel; and areturn spring means attached to the pawl and biased to pivot the pawl incounterclockwise direction, said pivotal movement of the pawl causingengagement of the projection on the other shank with thecounterclockwise facing flank of a tooth upon deenergization of theelectromagnetic means thereby turning the ratchet wheel in clockwisedirection.
 2. The stepping device according to claim 1 wherein a secondprojection is provided on said other shank also, said second projectionbeing correlated with the first projection on the other shank so thatboth said projections on the other shank simultaneously engageoppositely facing flanks of teeth in a second predetermined angularposition of the ratchet wheel thereby locking the wheel in said secondangular position, the first and second projection on said other shankbeing so disposed that the forces simultaneously applied to the flanksof the respective two teeth also extend approximately through therotational axis of the ratchet wheel.
 3. The stepping device accordingto claim 1 wherein the peripheral outline of said projections on theshanks and of the valleys between the teeth of the ratchet wheel are socorrelated that said protrusions engage valleys with play therebypreventing jamming of the projections in the valleys.